There are many things that annoy people on blogs but here are just some of them:
Colour
Some blogs use crazy colours. Making their background white and then having light gray letters. That does not make sense. Colours can put people off your blog.
Ads
We all need to make or have money but just blend your ads in your blog. Its both annoying when they stand out to much.
Flash
Flash sucks. Anything that moves while you are trying to read something sucks.
Loading time
Your blog should at least load before the end of earth.
Something else that annoys people is poor grammar and punctuation.
Like yours.
"Making their background white and then having light gray letters. That does not make sense."
The first sentence should say "Make your background white and have gray letters." Also, these two sentences do not need to be next to each other.
UNLESS you are saying that having a white background and light gray letters does not make sense. But you also say not to have color.
Hey, and go back and put in a few periods, ok?
The following are not sentences; they are run-ons.
"Colour Some blogs use crazy colours."
"Ads We all need to make or have money but just blend your ads in your blog." This sentence also needs a comma before "but".
"Loading time Your blog should at least load before the end of earth. "